This invention pertains to a tube positioning tool and method for its use. It pertains particularly to an elongated hydraulically-operated tool device useful for remotely axially positioning a tube in interfitting engagement with an existing tube, and to a method for using the tube positioning tool for remotely aligning and positioning a replacement tube.
In steam generators such as used for nuclear power plants, bundles of U-shaped heat exchange tubes are usually welded into a relatively thick tube sheet. During operation of such steam generators over an extended period of time, such as 10 years or more, a corrosive sludge material forms and accumulates on the inner upper surface of the tube sheet. This accumulated sludge material causes corrosion of the tube to an extent of potential or actual tube failure. To correct this serious problem without the undesired replacement of the heat exchanger, it is necessary to remove the old deteriorated tube end portions from the tube sheet and replace them with new tube portions which are remotely positioned and welded pressure tightly into place, without removing and dismantling the entire heat exchanger assembly. However, because of the remote relatively inaccessible location of the tubes and the radioactive environment which is usually involved, such tube replacement is very difficult to accomplish reliably and safely. Thus, a suitable solution to this problem has been needed, particularly for heat exchangers used in the nuclear power industry.
Some tools for tube alignment have been previously developed in the prior art. For example, a simple tube alignment device is disclosed by U.S. Pat. No. 914,743 to McDonald. Another tube alignment device is disclosed by U.S. Pat No. 2,429,053 to Forbes for end alignment of adjacent pipes prior to butt welding them together, and also by U.S. Pat. No. 2,730,604 to Eberle et al. U.S. Pat. No. 2,767,677 to Johnson et al discloses a jig for alignment of slip-on flanges on a pipe prior to welding them in place. However, none of these prior art devices has been found suitable for remotely axially positioning a tube portion in axial alignment and engagement with an existing tube, using hydraulic pressure. Accordingly, the present invention provides a special tube positioning tool which, after remote removal of damaged tubes from a heat exchanger, provides for their remote replacement with a new tube suitably aligned and inserted into the existing tube, and provides a method for using the tube positioning tool of the present invention to accomplish such remote tube alignment and positioning.